1) Field of the Invention
The present invention relates to a stacked layered core used in a variety of motors and a method for manufacturing the stacked layered core, and more particularly, to a stacked layered core having a stacked core body including a plurality of core plates stacked together and a dielectric film coated over an external surface of the stacked core body and a method for manufacturing the same.
2) Related Art
Generally, a stacked layered core used in a variety of motors is formed from a plurality of thin plate-like core plates 1 shown in FIG. 8, for example, that are stacked together, as shown in FIG. 9. FIGS. 8 and 9 show a stacked layered core C for an outer rotor type motor, and core plates 1 that compose the stacked layered core C. The stacked layered core has a circular connection based section 1a provided at a central portion thereof and a plurality of salient pole sections 1b that are outwardly, radially extending in a radial direction from an outer peripheral surface of the circular connection based section 1a. A fixing-side peripheral surface 1c on the internal peripheral side of the circular connection base section 1a, i.e., an internal bore of the circular connection base section 1a, engages a holder (not shown) whereby the stacked layered core is affixed to the holder.
A dielectric film is coated over an external surface of the stacked layered core C by a powder painting or an electrodeposition painting. Driving coils (not shown) are wound about the salient pole sections 1b over the dielectric film. When the dielectric film is formed, a core retaining jig 2 shown in FIG. 5 and FIG. 6 is used to support the entire body of the stacked layered core C. More concretely, the core retaining jig 2 has a boss section 2a and three protruded sections 2b radially protruding from the boss section 2a.
The protruded sections 2b of the core retaining jib 2 are abutted to the internal surface of the connection base section 1a of the stacked layered core C, in other words, to the fixing side peripheral surface 1c provided on a side opposite to the side where the protruded salient poles 1b protrude, whereby the entire body of the staked layered core C is supported by the core retaining jig 2.
Then,. one pair of shaft sections 2c provided on both sides of the boss section 2a of the core retaining jig 2 are set at a pair of screw conveyors 3, 3 provided in a painting apparatus, as shown in FIG. 5. Then, the screw conveyors 3 are rotatably driven to transfer the stacked layered core C together with the core retaining jig 2, to paint a dielectric film as described above. At this moment, as shown in FIG. 10, the protruded sections 2b of the core retaining jig 2 are in contact with the fixing-side internal peripheral surface 1c of the circular connection base section 1a of the stacked layered core C. When the painting of the dielectric film 4 is completed, one of the protruded sections 2b that is capable of moving in a radial direction is pushed toward the center of the core retaining jig 2. As a result, the other two protruded sections 2b are separated from the fixing-side internal peripheral surface 1c as shown in FIG. 11, such that the core retaining jig 2 can be removed from the stacked layered core C.
However, at a portion of the stacked layered core C from where the core retaining jig 2 is removed, in other words, at a portion of the stacked layered core C that has been in contact with each of the protruded sections 2b, a bump 4a of the dielectric film 4 is formed in the form of a bur.
Therefore, in order to maintain the internal dimension of the fixing-side internal peripheral surface 1c of the stacked layered core C at a high precision level, a finishing process in which the bump sections 4a are removed or compressed needs to be performed. Also, when the core retaining jig 2 is removed, each of the protruded sections 2b of the core retaining jig 2 may come in contact with various portions of the stacked layered core C, with the result that the dielectric film 4 may be cut or scratched, which is the major cause of poor paint quality.
Furthermore, portions that have been in contact with the protruded sections 2b of the core retaining jig 2 would not be painted with the dielectric film 4, and therefore would remain to be exposed. Such portions would likely be rusted. Accordingly, a sealing material such as an adhesive may be used to cover the non-painted portions depending on the requirements. However, in this case, the sealing material may form bumps, which results in irregular internal diameters in the internal bore of the stacked layered core C.
It is an object of the present intention to provide a stacked layered core in which a dielectric film can be readily formed at a high precision and a method for manufacturing the same.
In accordance with one embodiment of the present invention, a stacked layered core may include a core body formed from a plurality of core plates stacked in layers, each of the core plates having a connection base section formed in a circular shape and a plurality of salient pole sections radially extending from an external peripheral surface of an internal peripheral surface of the connection base. The circular connection base section has a fixing-side peripheral surface on the opposite side of the salient pole sections. At least one retaining recessed section is provided in the fixing-side peripheral surface of the connection base section. A dielectric film is formed over an external surface of the core body. In one aspect of the present invention, the retaining recessed section has a depth greater than a thickness of a bump portion of the dielectric film. that may be formed in the retaining recessed section such that the bump portion of the dielectric film is contained inside the retaining recessed section.
In accordance with the present invention, even when bump portions of the dielectric coating film may be formed, they are formed inside the retaining recessed section and therefore do not protrude from the supporting recessed sections. Furthermore, although damages may be caused by protruded sections of a core retaining jig that is used to support. the stacked layered core when the core retaining jig is removed, such damages are generated only inside the retaining recessed sections formed in the connection base section of the stacked layered core. Therefore, the bump portions of the dielectric coating film and the damaged portions do not affect the diametrical dimensions of the stacked layered core at all when the connection base section of the stacked layer core is affixed to a bearing holder of a motor, and therefore the productivity of stacked layered cores can be improved.